Electrical gremlins

Thought I'd share my electrical gremlin journey so far, with some still tbc details!

Starter issues:
Short version: intermittent starter issues, including no power on key turn, or rough start,engine code referring to circuit 87, and algorithm error.

Replaced battery - no difference.

Found:
- slight corrosion on 3 relays, very slight -light blue colouring at base of pins.
- A lot of rust around nuts on power distribution terminals
- a melted insulation sheath on starter cable (suspecting 'common' y cable failure on sprinter)

So far - replaced all relays and cleaned board with electrical contact cleaner.

Next steps is replacing terminals and nuts for nice clean connections.

Upgrade y cable but mechanic wants to do that as he wants to explore the melted insulation to make sure no other faults in the line.

Reverse camera:
- didn't like the head unit and suspected parasitic drain, so just disconnected it as reverse camera wasn't working anyway.
- pulled off rear left light out of interest and found a loose red cable with tape on it. Not sure if the tape used to hold it in place, or if it has been removed and insulated for a good reason. Can't see anywhere it might have been connected to, but suspect this is the 12v live for the reverse camera. Further tests to be conducted! Thinking of having the boss put it into reverse and find the reverse live, splice it in, and see does that bring the camera to life.

If anyone has any suggestions around anything I'm all ears! Just figured a problem shared is a problem halved

Have photos of everything if of interest too!

Sorry, 3 posts talking to myself is excessive....

HOWEVER I realised my error in that the split relay is fused... Which would've presumably broken if an excessive amperage went through.

I will be checking that though...

And yes, I have started a picture of a wiring diagram I'll eventually get to share with you lovely folk.

Yep, epever mppt controller!

Connected to panels and battery, but 12v systems connect to battery not controller!

Have you checked your earthing arrangements?

And all the battery pole connections, remove lean refit, there will also probably be a multi wire earth/ground connection around the engine bay and another for the Habitation system. All worth looking at.

With the amount of rust around, I would think/suggest you have serious earth problems, also as I have suggested, you should check all the Earth/Grounding around the Van.
Before you do anything else, If you have a set of jumpleads, connect one from battery earth ( make sure it's clean) to the body of the starter and see if that helps with the starting, that will give you a clear indication if you have a bad engine to chassis grounding, have someone try starting while you watch that there is no arcing from either the battery or starter body,